media: uvcvideo: Handle errors from calls to usb_string

On a Webcam from Quanta, we see the following error.

usb 3-5: New USB device found, idVendor=0408, idProduct=30d2, bcdDevice= 0.03
usb 3-5: New USB device strings: Mfr=3, Product=1, SerialNumber=2
usb 3-5: Product: USB2.0 HD UVC WebCam
usb 3-5: Manufacturer: Quanta
usb 3-5: SerialNumber: 0x0001
...
uvcvideo: Found UVC 1.10 device USB2.0 HD UVC WebCam (0408:30d2)
uvcvideo: Failed to initialize entity for entity 5
uvcvideo: Failed to register entities (-22).

The Webcam reports an entity of type UVC_VC_EXTENSION_UNIT. It reports a
string index of '7' associated with that entity. The attempt to read that
string from the camera fails with error -32 (-EPIPE). usb_string() returns
that error, but it is ignored. As result, the entity name is empty. This
later causes v4l2_device_register_subdev() to return -EINVAL, and no
entities are registered as result.

While this appears to be a firmware problem with the camera, the kernel
should still handle the situation gracefully. To do that, check the return
value from usb_string(). If it reports an error, assign the entity's
default name.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index 0a35d7c0d0a0a1017e2d610628cc6dbeaccda285..4c372965517d6d8c1fbe1978b4a1370f0c025192 100644 (file)
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -859,10 +859,8 @@ static int uvc_parse_vendor_control(struct uvc_device *dev,
                                               + n;
                memcpy(unit->extension.bmControls, &buffer[23+p], 2*n);
 
-               if (buffer[24+p+2*n] != 0)
-                       usb_string(udev, buffer[24+p+2*n], unit->name,
-                                  sizeof(unit->name));
-               else
+               if (buffer[24+p+2*n] == 0 ||
+                   usb_string(udev, buffer[24+p+2*n], unit->name, sizeof(unit->name)) < 0)
                        sprintf(unit->name, "Extension %u", buffer[3]);
 
                list_add_tail(&unit->list, &dev->entities);
@@ -986,15 +984,15 @@ static int uvc_parse_standard_control(struct uvc_device *dev,
                        memcpy(term->media.bmTransportModes, &buffer[10+n], p);
                }
 
-               if (buffer[7] != 0)
-                       usb_string(udev, buffer[7], term->name,
-                                  sizeof(term->name));
-               else if (UVC_ENTITY_TYPE(term) == UVC_ITT_CAMERA)
-                       sprintf(term->name, "Camera %u", buffer[3]);
-               else if (UVC_ENTITY_TYPE(term) == UVC_ITT_MEDIA_TRANSPORT_INPUT)
-                       sprintf(term->name, "Media %u", buffer[3]);
-               else
-                       sprintf(term->name, "Input %u", buffer[3]);
+               if (buffer[7] == 0 ||
+                   usb_string(udev, buffer[7], term->name, sizeof(term->name)) < 0) {
+                       if (UVC_ENTITY_TYPE(term) == UVC_ITT_CAMERA)
+                               sprintf(term->name, "Camera %u", buffer[3]);
+                       if (UVC_ENTITY_TYPE(term) == UVC_ITT_MEDIA_TRANSPORT_INPUT)
+                               sprintf(term->name, "Media %u", buffer[3]);
+                       else
+                               sprintf(term->name, "Input %u", buffer[3]);
+               }
 
                list_add_tail(&term->list, &dev->entities);
                break;
@@ -1027,10 +1025,8 @@ static int uvc_parse_standard_control(struct uvc_device *dev,
 
                memcpy(term->baSourceID, &buffer[7], 1);
 
-               if (buffer[8] != 0)
-                       usb_string(udev, buffer[8], term->name,
-                                  sizeof(term->name));
-               else
+               if (buffer[8] == 0 ||
+                   usb_string(udev, buffer[8], term->name, sizeof(term->name)) < 0)
                        sprintf(term->name, "Output %u", buffer[3]);
 
                list_add_tail(&term->list, &dev->entities);
@@ -1052,10 +1048,8 @@ static int uvc_parse_standard_control(struct uvc_device *dev,
 
                memcpy(unit->baSourceID, &buffer[5], p);
 
-               if (buffer[5+p] != 0)
-                       usb_string(udev, buffer[5+p], unit->name,
-                                  sizeof(unit->name));
-               else
+               if (buffer[5+p] == 0 ||
+                   usb_string(udev, buffer[5+p], unit->name, sizeof(unit->name)) < 0)
                        sprintf(unit->name, "Selector %u", buffer[3]);
 
                list_add_tail(&unit->list, &dev->entities);
@@ -1085,10 +1079,8 @@ static int uvc_parse_standard_control(struct uvc_device *dev,
                if (dev->uvc_version >= 0x0110)
                        unit->processing.bmVideoStandards = buffer[9+n];
 
-               if (buffer[8+n] != 0)
-                       usb_string(udev, buffer[8+n], unit->name,
-                                  sizeof(unit->name));
-               else
+               if (buffer[8+n] == 0 ||
+                   usb_string(udev, buffer[8+n], unit->name, sizeof(unit->name)) < 0)
                        sprintf(unit->name, "Processing %u", buffer[3]);
 
                list_add_tail(&unit->list, &dev->entities);
@@ -1116,10 +1108,8 @@ static int uvc_parse_standard_control(struct uvc_device *dev,
                unit->extension.bmControls = (u8 *)unit + sizeof(*unit);
                memcpy(unit->extension.bmControls, &buffer[23+p], n);
 
-               if (buffer[23+p+n] != 0)
-                       usb_string(udev, buffer[23+p+n], unit->name,
-                                  sizeof(unit->name));
-               else
+               if (buffer[23+p+n] == 0 ||
+                   usb_string(udev, buffer[23+p+n], unit->name, sizeof(unit->name)) < 0)
                        sprintf(unit->name, "Extension %u", buffer[3]);
 
                list_add_tail(&unit->list, &dev->entities);